mk: quote KERNELCC to allow ccache build
mk: quote KERNELCC to allow ccache build

Otherwise building with KERNELCC="ccache gcc" will fail:
 ccache: invalid option -- 'p'

Signed-off-by: Simon Kagstrom <55f06860226d5500245ed5c8a62a0a8911dc9a7e@netinsight.net>
Acked-by: Olivier Matz <dfcc1510895413197abb4336e39bb0a3906cba71@6wind.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk